Rostock (delta robot 3D printer) fitted with Airtripper’s bowden extruder

About The Airtripper Extruder

The Airtripper’s direct drive bowden extruder for 3d printers has been a large success, which has allowed makers & builders to easily add an extruder to their custom 3d printer. Its simple bracket design means the extruder can be attached to most surfaces and T-slot type extrusions, and its compact design easily allow for multi hot end set-ups. The bowden extruder’s popularity was especially boosted when it was used on the first Delta Robot 3d printer called Rostock by Johann C. Rocholl. The Airtripper’s bowden extruder was originally designed to replace the Sumpod 3d printer extruder.

After writing the “3D Printer Extruder Filament Drive Gear Review & Benchmark” there is no longer any doubt about the capabilities of direct drive extruders when using recommended stepper motor and drive gear. With better stepper driver tuning, the MK8 drive gear could probably push more force than what I’ve recorded, and if you are only going to be using 1.75mm filament then a direct drive extruder is all you need for most 3d printing operations.

Available On Ebay

The Airtripper’s Bowden Extruder V3 BSP Edition is sold on Ebay by me as a kit with plastic parts and fittings, with optional PTFE tube and extra BSP fitting. The extruder kit is also offered without the plastic parts which allows the purchaser to get the bits from one place in needed quantities and 3d print the plastic parts themselves. My Ebay listings.

Airtripper’s 3D Printer Direct Drive Bowden Extruder BSP Edition

Additions & Tweaks

The latest batch of additions and tweaks was driven by requests to adapt the extruder to accept a BSP push in fitting. Other makers had successfully adapted the extruder to accept a type a of push fitting, but I wanted to use the most popular and most widely available push fittings and made my own adaptation. So the bowden extruder can now be fitted with the 1/8″ BSP 4mm straight fitting.

A view of the 1/8″ 4mm BSP Fitting With Set Screw, and a view of the 4mm Pipe Connector

The second addition to the extruder, after the BSP socket add-on, is the pipe bracket. The pipe bracket allows a 4mm tube to be connected to the extruder so that filament can be gently guided from the spool to the extruder. A separate tube bracket, the new additional part, is used to fix the other end of the tube near to the filament spool. The tube bracket was a separate add-on with the last extruder version but now the tube bracket is integrated in the latest extruder body design.

Some tweaks was made to the extruder fixing bracket so that it 3d printed more neatly; you can use the Thingiverse STL viewer to compare this extruder version to the last version. Another tweak was made to the  idler housing. It was found that the idler housing was prone to cracking when printed with brittle filament. So the tweak included widening the idler housing and thickening the walls; this has led to a shorter axle. The axle now drops to rest into a deeper sockets so that once the axle and bearing is pushed into position the axle does not constantly push into the idler housing walls, reducing stress and cracking over time.

3D Printer Bowden Extruder – Parts

Airtripper’s Bowden Extruder 3D Printed Parts

Four 3d printed parts are required to complete the bowden extruder plus an optional part called the tube bracket. The tube bracket allows for a PTFE tube, or other 4mm outer diameter tube, to fit between the bracket and the bowden extruder; this allows the extruder to pull filament from the spool, guided by the tube, from different possible spool location around the printer.

3D Printing The Parts

Skeinforge had been my first choice for printing the bowden extruder parts for some time but Cura has shown to do a better slicing job – and much faster too, and with the ability to print a tray of parts one part at a time, means Stringing is kept to a minimum. I have used Slic3r in the past and found that the extruder body thin walls don’t fill correctly, however, the latest Slic3r versions may provide better results.

I’ve 3d printed the bowden extruder using only PLA filament and can’t really comment on how well the extruder parts will print using other filament materials. There have been reports that ABS filament works well enough but there have been a couple of reports about issues with printing the idler bearing housing correctly.

A print layer height of 0.25mm is always set with my own extruder parts print, with top and bottom layers set to 0.75mm. The fill density is normally set to 25 percent, and with the print speed set to 24mm/s, all the parts will take around three to three and a half hours to print.

Non 3D Printable Parts

Airtripper’s 3D Printer Bowden Extruder Metal Parts

A full description and quantity of the parts that are shown in the image above:

• 1 x M3 x 25mm S/S Cap Screw Allen Bolt.
• 2 x M3 x 30mm S/S Cap Screw Allen Bolt.
• 2 x M3 x 45mm S/S Cap Screw Allen Bolt.
• 1 x M3 x 6mm S/S Button Head Allen Bolts.
• 1 x M3 x 10mm Screw
• 4 x M3 Stainless Hex Full Nuts.
• 2 x M3 washers.
• 1 x 22mm of 1/4″ 6mm id Rubber Diesel Hose Tubing Line.
• 1 x 608 ZZ [8 x 22 x 7] Roller Skate Ball Bearings.
• 1 x 1/8″ BSP Male to 4mm Straight Push In Pneumatic Fitting

MR105ZZ Ball Bearing for the stepper motor axle is optional with drive gears such as MK7 and MK8

The above parts are required to assemble the bowden extruder to the stepper motor and allow for the bowden tube to be attached. If you own a Dremel type tool you can cut the 6mm and the 25mm screws from the longer versions if desired.

I’ve continued to use the rubber tube as the idler bearing pre-loader because it allowed for plenty of space to remove the idler housing from the extruder for filament changing. I’ve tried using springs and it was difficult to get the springs over the idler housing hooks.

Caution needs to be taken when fitting the BSP fitting to avoid splitting the extruder body. The threads on the BSP fitting provide a good grip inside the fitting socket on the extruder, so there is no need to tighten the set screw too much. The set screw only needs tightening just enough to hold the fitting in place.

3D Printer Bowden Extruder – Recommended

PTFE 4mm x 2mm Tube Preparation For Bowden Extruder To Reduce Filament Snagging.

Since this is a bowden extruder, you will almost certainly be using a length of PTFE tube between the extruder and the hot end. The extruder is designed to take PTFE tube (4mm OD x 2mm ID) and 1.75mm filament, 1/8″ BSP Male to 4mm push fitting is used to connect the tube to the extruder.

As shown in the picture above, to avoid snagging when loading new filament, it is recommended to taper the end of the tube which can be done with a drill bit. Some snagging will occur occasionally but changing the PTFE tube alignment inside the fitting with one hand while loading the filament will help get the filament through the connector.

Before loading new filament into the extruder, straighten the end of the filament as much as possible so the end of the filament does not snag inside of the BSP fitting. Snip the end of the filament if not cut square.

3D Printer MK8 Extruder Filament Dive Gear Benchmark, Recommended For Direct Drive PLA Extruder

Along with a high torque stepper motor, the MK8 drive gear is recommended for the direct drive bowden extruder. As shown in the tests here, a good stepper motor / drive gear combination will provided plenty enough torque to drive 1.75mm filament. It will be difficult to solve 3d printing problems or even to calibrate the printer properly without the correct stepper motor and drive gear behind the extruder.

Extruder Stepper Motor SY42STH47-1684B

The stepper motor I use with my own extruder set-up is the SY42STH47-1684B (Holding Torque (Kg.cm) 4.4) and you will find this stepper on the RepRap NEMA 17 Stepper motor Wiki page.

Due to the grip provided by the MK7 and MK8 drive gear filament pulleys, it is no longer necessary to have the extra bearing on the stepper motor axle. The MR105ZZ Ball Bearing was previously used on the axle to take some load of the stepper motor internal bearings, but since the MK7 and the MK8 drive gears have excellent grip on the filament, it is not necessary to apply a heavy load on the axle with the idler bearing. These same stepper motors are used to drive pulley belts and may put a higher load on the axle than the extruder idler bearing itself.

Airtripper’s Direct Drive Bowden Extruder V3 BSP – Files

OpenSCAD Script File Code Snippet: preview_part = 1; // [1:Extruder,2:Idler,4:Strut,5:Axle,6:Tube Bracket]

However, should the STL files need to be compiled again, the OpenSCAD script file for the extruder is also available for download. At the minimum, you would only need to change one line of code to compile an STL file for each of the bowden extruder parts.

preview_part = 1; // [1:Extruder,2:Idler,3:Idler with brim,4:Strut,5:Axle,6:Tube Bracket,7:All Parts]

You’ll find the above line of code in the OpenSCAD script file at the top of the page after a few lines of comments. Basically, to select a model to edit or compile to STL, change the number assigned to the preview_part variable with the number assigned to the model; the image above shows a number assigned to each bowden extruder part model.

File Downloads

Thingiverse

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Related Articles

3D Printer Extruder Filament Drive Gear Review & Benchmark

Airtripper’s Bowden Extruder V3 – Updated Design

3D Printer Surgery #4 Extruder Upgrade Part 3

Airtripper’s 3D Printer Direct Drive Bowden Extruder V3 BSP

Airtripper’s Direct Drive Bowden Extruder V3

The Airtripper’s Direct Drive Bowden Extruder is now at version 3 with the design files ready to download from Thingiverse. A lot of work went into the design to improve the usabillity and the look of the extruder. The design is stronger with a much cleaner 3d printed finish, and filament changing is now much easier than before.

The bowden extruder was originally designed to fit the Sumpod 3d printer to replace the bulky MDF extruder housing that was awkward to use. However, the bowden extruder can be used for other 3d printers making use of it’s simple bracket, and the extruder has been popular with the Rostock delta 3d printer. A tube bracket is now availble for attaching to the bowden extruder to help guide the filament from the filament spool. more about that here at Sumpod 3D Printer Filament Handling for Bowden Extruder.

You will find more about this bowden extruder on the following page: Bowden Extruder Upgrade Part 3.

The popularity of The Airtripper’s bowden extruder was boosted when the extruder was included in the development of the awesome Rostock 3D Printer (delta robot 3D printer). To see the bowden extruder in action on the Rostock, watch the youtube clip below.

Click here to view the video on YouTube.

Bowden extruder V3 Update Details

A number of updates were made to the bowden extruder design with some minor updates on the strut and idler housing.

To get a better fill between perimeters around the screw holes, the rounded ends on the strut have been increased to 10mm in diameter to improve print quality on wider 3d printer settings.  A small taper was added to the edge of the idler bearing housing to make it easier to slide the rubber tube over the preloader hook.

1. The filament drive gear housing has been filled-in to improve overall print quality by minimizing stringing.
2. Filament guide funnel size increased and angled for (a) a more gentle filament bend around the drive gear and for (b) easier filament threading.
3. Holes opened up and angled to give the idler preload screws better clearance from the idler housing hooks.
4. M4 nut for bowden cable (PTFE tube) now drops in to position much easier than before, also, reduced filament snagging when threading into the bowden cable.
5. Screw column housing lowered and widened at the top to minimize shrinkage and deformation. The M3 screw now drop in without drilling out, although a 25mm screw is now required instead of a 30mm. However, a 30mm screw will fit with a washer so the screw cap does not drop into the recess.
6. Holes removed from the fixing bracket to improve overall 3d print quality.
7. The filament in-feed bracket is re-designed for a much cleaner look and is now attached to a screw column for added strength.
8. A spacer is added so that extra washers are no longer needed.

Bowden Extruder V3 Parts List & Files

Most of the items below can be acquired cheaply from Ebay. The MR105ZZ Ball Bearing is optional but recommended, and the Rubber Diesel Hose can be replaced for coil springs. The M6 nuts, bolts & washers are for attaching the extruder to the Sumpod 3d printer or any other printer with similar fixing arrangement, just decide what length of bolts you need.

Extruder 3D Design Files

All the files for this extruder project are on Thingiverse for download. I’ve Supplied STL files that combine selected 3d objects for printing in one session. This is good for the smaller 3d objects because the printed layers will be given more time to cool. You can download the files from here:

http://www.thingiverse.com/thing:35404

Special Parts

• Nema 17 Stepper Motor. Since this extruder is a direct drive type, a powerful stepper motor will be needed. Point your browser to http://reprap.org/wiki/Stepper_motor for a good source of stepper motor information.
  
• Filament Drive Gear. For direct drive extruders, I can only recommend the MK7 drive gear at this point. If this does not work, you probably have Hot End issues. Starting with a tried and tested drive gear will help with your extruder system trouble shooting.
  

Screws, Nuts & Washers

• 1 X   M3 x 25mm S/S Cap Screw Allen Bolt.
• 2 X   M3 x 30mm S/S Cap Screw Allen Bolt.
• 2 X   M3 x 45mm S/S Cap Screw Allen Bolt.
• 1 X   M3 x 6mm S/S Button Head Allen Bolts.
• 3 X   M3 Stainless Hex Full Nuts.
• 1 X   M4 Stainless Hex Full Nuts.
• 2 X   M3 washers.
• 2 X   M6 S/S Hex Head Bolts.
• 2 X   M6 S/S Flat Form B Washers.
• 2 X   M6 S/S Hex Full Nuts.

Ball Bearings

• 1 X   608 ZZ [8 x 22 x 7] Roller Skate Ball Bearings.
• 1 X   MR105 ZZ Model Miniature Ball Bearing 5 x 10 x 4mm.

Tube

• 1 X   PTFE Tube 4mm x 2mm.
• 1 X   1/4″ 6mm id Rubber Diesel Hose Tubing Line.

Printing the Bowden Extruder

Direct Drive Extruder 3D Printed Parts

As a guide for printer set-up, I’ll list some of the settings used to compile the G-code. The toolchain I normally use includes OpenSCAD, Skeinforge, Printrun/Pronterface and Marlin. The settings listed below will be those used in Skeinforge, just the notable settings are included that works for this 3d print. Printing thicker layers and adding extra shells could create gaps in some surface layers, especially around screw holes that are close to a surface edge.

• Carve: Layer Height = 0.25
• Dimension: Filament Diameter = 1.75
• Fill: Extra Shells on Alternating Solid Layers = 2, Extra Shells on Base Layers = 1, Extra Shells on Sparse layer = 1, Infill Solidity (ratio) = 0.25

The STL files should be all you need to print off the extruder successfully, and I’ve provided extra STL files that will allow you to print a pair of selected items or all the items in one go.

3d model images have been uploaded to Thingiverse to help identify which STL files have multiple objects in them. The STL files rendered to images by Thingiverse don’t clearly show the files with multiple 3d objects.

Assembling the Bowden Extruder

The original assembly instructions are still valid for this bowden extruder update and you can find it here: Extruder Upgrade Part 3.

To add to the original instructions

The bowden extruder V3 bill of materials is slightly different from the last version because of a couple of small changes made to the extruder main body. However, all the parts used to assemble previous versions of the extruder will still fit the new version without buying new parts.

As mentioned above (bowden extruder update details), an M3 x 25mm screw is now required for one of the screw posts for attaching the extruder to the stepper motor. However, an M3 x 30mm screw can still be used if a washer is added to the screw before inserting in to the screw column. This will shorten the screw enough to fit the stepper motor body.

Direct Drive Extruder Stepper Motor with Gear, M5 washers and Ball Bearing. Notice the bearing with electrical insulation tape to increase diameter.

The bowden extruder features an axle bearing support for the optional MR105 ZZ ball bearing to spread the load on the stepper motor shaft. Because of variations in 3d printer outputs, it may be necessary to add a bit of extra diameter to the ball bearing. When assembling the bowden extruder, take note of the amount of contact between the ball bearing and the bearing support. If you don’t think there is enough contact, try a piece of electrical insulation tape to add some diameter to the ball bearing. Add as many tape layers as needed to get good contact.

Some types of filament drive gears, after lining them up with the filament on the stepper motor shaft, will leave a gap between the ball bearing and the drive gear. For proper stepper motor shaft support, the ball bearing should be positioned at the end of the shaft. This position can be maintained by adding M5 size washers to fill the gap between the bearing and the filament drive gear.

Related Topics

Sumpod 3D Printer Filament Handling for Extruder
Bowden Extruder Upgrade Part 3
Bowden Extruder Upgrade Part 2
Bowden Extruder Upgrade Part 1

Airtripper’s Direct Drive Extruder V3 Assembled View from Front	Airtripper’s Direct Drive Extruder V3 Assembled View from Back
Airtripper’s Direct Drive Extruder V3 Fitted without washer on M3 x 25mm screw	Airtripper’s Direct Drive Extruder V3 Fitted with washer on M3 x 30mm screw
Raptor Universal Filament Drive Gear from QU-BD, CNC machined from a brass alloy and shipped with the MBE Extruder.	Airtripper’s Direct Drive Bowden Extruder V3 Fitted to Sumpod 3D Printer

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Airtripper’s Bowden Extruder V3

The new 3D printer 1.75mm filament extruder upgrade is now complete, all the tweaks mentioned in the Extruder Upgrade Part Two are now built in to the unit, plus extra improvements was made to the overall design, including a newly designed idler to accept the cheaper 608 ZZ Skate Bearing to simplify assembly and to keep the overall cost down. All the project files are now on Thingiverse, STL files and the OpenSCAD 3D script file. Check out the rest of this post for bill of materials, printing and assembly tips.

This 3D printer extruder is design to fit the SUMPOD 3D printer without further modification which makes it an ideal upgrade for SUMPOD users. However, due to it’s simple fixing bracket and bowden feed, the extruder can be easily added to the other 3D printer designs.

3D Printer 1.75mm Filament Extruder

The extruder, because of it’s compact size, is an ideal solution for multi-coloured printing, and also ideal for multi-nozzle 3D printers.

Rubber Pinch Roller
I’ve been testing a rubber pinch roller idler for a while now, and after close inspection of the roller, I can’t see any damage or deformation in the rubber. In my opinion, the rubber pinch roller has performed very well and performed at least as good as a bare ball bearing. However, I’m not going to recommend it for this extruder because I can’t yet provide details that proves it offers better performance than a bare ball bearing idler. For the extra cost to implement it, some proof of superior performance over ball bearing is necessary before recommending it. You will find more details and pictures about the rubber pinch roller in Extruder Upgrade Part 2.

Sumpod 3D Printer Extruder Upgrade

SUMPOD 3D Prototyping Printer – View from Rear

I’m recommending this 3D printer extruder as a replacement for the original SUMPOD extruder for the benefits including the following:

• The filament is pushed over a ball bearing instead of a plunger, reducing friction.
• Filament is guided through the extruder mechanism without needing to disassembling the extruder.
• A lot quicker and easier to change filament.
• It’s open and accessible design makes it easier to trouble shoot, and to visually detect signs of filament slippage.
• Easy to mount on the SUMPOD using the original extruder mount points with M6 nuts and bolts.
• The new extruder is much lighter and a lot more compact making the SUMPOD more evenly weighted.
• Improves the overall look of the SUMPOD.
• Easy to attach a second extruder for dual nozzle set up and multi coloured printing.
• Option to add a shaft ball bearing that may extend the life of the stepper motor by reducing the load on the internal stepper motor bearings.

Printing The Parts

3D Printer Extruder Body, printed at 0.2mm layer height.

3D Printer Extruder Printed Parts – Idler Body, Strut and 8mm Ball Bearing Shaft.

Well, there are four items to print, the main body, a support strut, idler housing and an 8mm ball bearing shaft. There will be an STL file for each item so that they can be printed separately, this will produce cleaner parts, especially if you have a bit of trouble with oozing and stringing. For the ball bearing support to be properly aligned with the stepper motor shaft bearing, the 3d printer build platform needs to be as level as it can be for printing the main extruder body.
All the printed parts were printed slowly with a fast travel feed rate with the layer height set to 0.2mm, this helped to reduce the working pressure in the nozzle which made cleaner prints, stringing and oozing kept to a minimum. For these 3d prints I used Skeinforge and Pronterface, and for the 3d printer firmware, Marlin Ver. 1 RC2.

Bill of Materials
All the parts are available from Ebay apart from the brass gear insert, if you are a SUMPOD owner, then you will have the brass gear insert already. The small shaft support ball bearing (MR105 ZZ) is optional but may improve the life of the stepper motor if fitted, also the M3 6mm screw is also optional since three screws is enough to attach the stepper motor to the extruder base. SUMPOD users require two M6 30mm screws to attach the extruder to the 3D printer, longer screws provided with the printer could be cut down to fit.

1.75mm 3D Printer Extruder Parts

The extruder requires M3 Allen Bolt Cap screws, three of 30mm and two of 45mm, these come with a smooth shaft and a limited amount of threaded shaft. To reduce cost, and you have a Dremel and eye protection, you can purchase all M3 screws at 45mm length, then cut three of them down to 34mm length (not including the cap) and fit them with M3 washers so that the caps don’t sink into the cap recess on the extruder body. Please note that the M3 45mm screws have been sized to fit the idler that is preloaded with 6mm i.d. diesel hose. You could use springs instead of diesel hose, in which case, you’ll need to size the M3 screws to fit accordingly.

Part sources and price is provided as a guide only and I’m not affiliated with any supplier on this post. Shopping around should help to reduce overall cost.

Full BoM List

1. 1 X   MR105 ZZ Model Miniature Ball Bearing 5X10X4 – Ebay
2. 1 X   1/4″ 6mm id Rubber Diesel Hose Tubing Line – Ebay
3. 1 X   5mm Plain Insert – Maritime Models – 1.80 + p&p
4. 3 X   M3 x 30 S/S Allen Bolt Cap Screw – Ebay
5. 2 X   M3 x 45 S/S Allen Bolt Cap Screw – Ebay
6. 3 X   M3 Stainless Hex Full Nuts – Ebay
7. 3 X   M3 washers – Ebay
8. 1 X   PTFE Tube 2X4mm – Ebay
9. 1 X   M4 Stainless Hex Full Nuts – Ebay
10. 2 X   M6 30mm Stainless Hex Head Bolts – Ebay
11. 2 X   M6 S/S Flat Form B Washers – Ebay
12. 2 X   M6 S/S Hex Full Nuts – Ebay
13. 1 X   608 ZZ [8 x 22 x 7] Roller Skate Ball Bearings – Ebay
14. 1 X   M3 x 6 Stainless Button Head Allen Bolts – Ebay
15. Files for 3d printable parts – Thingiverse

3D Printer Extruder Assembly

Some basic tools are required to complete the 3d printer extruder including, a file, drill bits to clean out the screw holes, and allen keys to assemble the extruder. Pliers may be required to grip the drill bits when reaming screw holes, and also to hold nuts while tightening screws and threading PTFE tube. The drill bits are used by hand for reaming so no power drill is required. Pictures are provided below to help with extruder assembly.

When preparing the PTFE tube to accept the M4 nut, file a taper around the end of the tube to make it easier to screw the nut on. Twist the nut back and forth a few times to get a good thread on the tube, and with the nut in place, used a 2mm drill bit to restore the tube’s inner diameter if necessary. Fit the nut, with the tube connected, in to the slot on top of the extruder and screw the tube one turn in to the nut to lock in place after testing for hole alignment with a piece of filament.

To prepare the idler preloader, cut a piece of diesel hose tubing to about 22mm long, then make two holes about 12mm apart for the M3 screws to go through. You can make the holes by pushing a thin shafted plus head screw driver through the rubber, and then move a drill bit back and forth to open up the holes enough to push the M3 45mm screws through. You may have to use pliers to hold the drill bit. Refer to the pictures below for further assembly details.

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3D Printer Extruder Base and Stepper Motor Assembly	3D Printer Extruder Strut Assembly
3D Printer Extruder Idler Preloader Assembly	3D Printer Extruder 608ZZ Ball Bearing Idler
3D Printer Extruder Bowden Tube Cable with Nut	3D Printer Extruder and Stepper Motor Assembled